The metric system uses the Celsius scale to measure temperature. However, temperatures
are still measured on the Fahrenheit scale in the U.S.

Water freezes at 0o Celsius and boils at 100o Celsius which is a difference
of 100o. Water freezes at 32o Fahrenheit and boils at 212o
Fahrenheit which is a difference of 180o. Therefore each degree on the
Fahrenheit scale is equal to 100/180 or 5/9 degrees on the Celsius scale.

Note: This lesson includes temperatures that use negative numbers. Negative
numbers follow a pattern that is opposite of positive numbers. The number -20 is
smaller than the number -10. Example of counting with negative and positive numbers:
-5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5